[PATCH] ima: more careful error checking in restore_template_fmt()

[Konsta Karsisto <konsta.karsisto@xxxxxxxxx>]

Fix a case where a failure in strdup() after a successful kzalloc()
could lead to a crash later on. Also, change the function signature
to allow returning an error code, which can be returned a the return
value of ima_restore_measurement_list().

Signed-off-by: Konsta Karsisto <konsta.karsisto@xxxxxxxxx>
---

Unfortunately, I'm not familiar with the ima kexec cofiguration,
and thus this has been compile tested only.

 security/integrity/ima/ima_template.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index 6aa6408603e3..6b1964cbcbf5 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -270,7 +270,7 @@ int __init ima_init_template(void)
 	return result;
 }
 
-static struct ima_template_desc *restore_template_fmt(char *template_name)
+static int restore_template_fmt(char *template_name, struct ima_template_desc **returned_desc)
 {
 	struct ima_template_desc *template_desc = NULL;
 	int ret;
@@ -279,23 +279,27 @@ static struct ima_template_desc *restore_template_fmt(char *template_name)
 	if (ret < 0) {
 		pr_err("attempting to initialize the template \"%s\" failed\n",
 			template_name);
-		goto out;
+		return ret;
 	}
 
 	template_desc = kzalloc(sizeof(*template_desc), GFP_KERNEL);
 	if (!template_desc)
-		goto out;
+		return -ENOMEM;
 
 	template_desc->name = "";
 	template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
-	if (!template_desc->fmt)
-		goto out;
+	if (!template_desc->fmt) {
+		kfree(template_desc);
+		return -ENOMEM;
+	}
 
 	spin_lock(&template_list);
 	list_add_tail_rcu(&template_desc->list, &defined_templates);
 	spin_unlock(&template_list);
-out:
-	return template_desc;
+
+	*returned_desc = template_desc;
+
+	return 0;
 }
 
 static int ima_restore_template_data(struct ima_template_desc *template_desc,
@@ -421,8 +425,8 @@ int ima_restore_measurement_list(loff_t size, void *buf)
 
 		template_desc = lookup_template_desc(template_name);
 		if (!template_desc) {
-			template_desc = restore_template_fmt(template_name);
-			if (!template_desc)
+			ret = restore_template_fmt(template_name, &template_desc);
+			if (ret < 0)
 				break;
 		}
 
-- 
2.17.1